10 experiments

8/13/2019 10 Experiments

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BusinessResearch Methods

William G. Zikmund

Chapter 12:Experimental Research


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Experiment

A research investigation in which conditions arecontrolled

One independent variable is manipulated(sometimes more than one)

Its effect on a dependent variable is measured

To test a hypothesis


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Basic Issues of Experimental

Design Manipulation of the Independent Variable Selection of Dependent Variable Assignment of Subjects (or other Test

Units) Control Over Extraneous Variables


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Experiment Treatment

Alternative manipulations of the

independent variable beinginvestigated


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Independent Variable

The experimenter controls independentvariable.

The variables value can bemanipulated by the experimenters to

whatever they wish it to be.


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Manipulation of Independent

Variable Classificatory Vs. continuous variables Experimental and control groups Treatment levels More than one independent variable


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Experimental Treatments

The alternative manipulations of theindependent variable being investigated


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Dependent Variable

Its value is expected to be dependenton the experimenters manipulation

Criterion or standard by which theresults are judged


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Dependent Variable

Selection e.g... sales volume, awareness, recall,

Measurement


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Test Units

Subjects orentities whoseresponse to theexperimentaltreatment aremeasured orobserved.


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Two Types of Experimental

Error Constant errors Random errors


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Establishing Control


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Physical Control

Holding the value or level of extraneousvariables constant throughout the course ofan experiment.

Statistical Control Adjusting for the effects of confounding

variables by statistically adjusting the valueof the dependent variable for each

treatment conditions.Design Control Use of the experimental design to control

extraneous causal factors. Eg. Demand


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Demand Characteristics

Experimental procedures that intentionallyhint to subjects something about the

experimenters hypothesis


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Demand Characteristics

Guinea pig effect

Hawthorne effect


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Field versus

Laboratory Experiments


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Field Vs. Laboratory Experiment


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Laboratory Experiment Field Experiment

Artificial-Low Realism

Few ExtraneousVariables

High controlLow Cost

Short Duration

Subjects Aware ofParticipation

Natural-High Realism

Many ExtraneousVariables

Low controlHigh Cost

Long Duration

Subjects Unaware ofParticipation


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Control Groups

Isolateextraneousvariation


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When does an Experiment haveInternal Validity?

Internal Validity - The ability of anexperiment to answer the question whetherthe experimental treatment was the solecause of changes in a dependent variable

Did the manipulation do what it was supposedto do?


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Factors Influencing Internal

Validity History Maturation Testing Instrumentation Selection Mortality


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Isolating Extraneous Variation

with a Control Group History Effects Maturation Effects Mortality Effects


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Type of Extraneous Variable Example

History - Specific events in theenvironment between the Beforeand After measurement that arebeyond the experimenters control

Maturation - Subjects changeduring the course of the experiment

Testing - The Before measure alerts

or sensitizes subject to nature ofexperiment or second measure.

A major employercloses its plant intest market area

Subjects becometired

Questionnaire

about the traditionalrole of womentriggers enhancedawareness of womenin an experiment.


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Instrument - Changes in

instrument result in response bias

Selection - Sample selectionerror because of differentialselection comparison groups

Mortality - Sample attrition; somesubjects withdraw from experiment

New questions about

women are interpreteddifferently from earlierquestions.

Control group andexperimental group isself-selected groupbased on preference forsoft drinks

Subjects in one groupof a hair dying studymarry rich widows andmove to Florida


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How can Internal Validity

Increase?


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Increasing Internal Validity

Control group

Random assignment

Pretesting and posttesting

Posttest only


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What are the Different Basic

Experimental Designs?


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Quasi-Experimental Designs

One Shot Design (After Only) One Group Pretest-Posttest Static Group Design


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One Shot Design (After Only) X O 1


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One Group Pretest-Posttest

O 1 X O 2


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Three Good Experimental Designs

Pretest - Posttest Control Group Design

Posttest Only Control Group

Solomon Four Group Design


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Pretest-Posttest Control Group Design

Experimental Group R O 1 X O 2

Control Group R O 3 O 4


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Posttest Only Control Group

Experimental Group R X O 1

Control Group R O 2


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One-Shot DesignInternal Validity Problems

History weak

Maturation weak

Testing not relevant

Instrumentation not relevant

Selection weak

Mortality weak


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One-Group Pretest-PosttestInternal Validity Problems

History weak

Maturation weak

Testing weak

Instrumentation weak

Selection controlled

Mortality controlled


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Static-Group DesignInternal Validity Problems

History controlled

Maturation possible source of

concern

Testing controlled

Instrumentation controlled

Selection weak

Mortality weak


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Pretest-Posttest Control

Internal Validity Problems History

controlled

Maturation controlled

Testing controlled





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Solomon Four-Group Design


controlled


Testing controlled





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Posttest-Only Control


controlled


Testing controlled





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Solomon Four Group Design

Experimental Group 1: R O 1 X O 2Control Group 1: R O 3 O 4Experimental Group 2: R X O 5 Control Group 2: R O 6


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Advanced Experimental Designs areMore Complex

Completely randomized Randomized block design Latin square Factorial


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Completely Randomized Design

An experimental design that uses a random process to assign subjects (test units) and

treatments to investigate the effects of onlyone independent variable.


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Completely Randomized Designs

Average minutesshopper spendsin store

Control:no music

Experimentaltreatment:slow music

Experimentaltreatment:fast music

16 18 12


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Independent Variable A

Group A Group B Group C

Level 1 Level 2 Level 3


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With a pretest posttest

Group A R O 1 X1 O2

Group B R O 3 X2 O4

Group C R O 5 X3 O6


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With a posttest

Group A R X 1 O1

Group B R X 2 O2

Group C R X 3 O3



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Randomized Block Design

An extension of the completely randomized

design in which a single extraneous variablethat might affect test units response to thetreatment has been identified and the effects

of this variable are isolated by blocking outits effects.


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Independent Variables

Control:no music

Experimentaltreatment

slow music

Experimentaltreatment:fast music

Mornings andafternoons

Evening hours B l o c

k i n g v a r i a

b l e

Randomized Block Design


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Factorial Design

An experiment that investigates the

interaction of two or more variables on asingle dependent variable.


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Independent Var i abl e 1

No Music

cart signs

Slow Music Fast MusicNo Music

Grocerycart signs

I n d

e p e n

d e n

t V a r i a

b l e 2


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Price Red Gold

$25 Cell 1 Cell 4$30 Cell 2 Cell 5$35 Cell 3 Cell 6

Package Design

Factorial Design -- Roller Skates


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Effects

Main effect The influence of a

single independentvariable on adependent variable.

Interaction effect The influence on a

dependent variable bycombinations of twoor more independentvariables.


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Men

Women

Ad A Ad B

65

65

70 60

Main Effectsof Gender

Main Effects of Ad

>

2 x 2 Factorial Design


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100

9080

70

60

50

40

3020

10 Ad A Ad B

Interaction Between Gender andAdvertising Copy


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Level 1 Level 2

Level 1

Level 2

Group A

Group DGroup C

Group B

I n d e p e n

d e n

t

V a r i a

b l e 2

Independent Variable 1

2 2 F t i l ith P t t


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Group A R O 1 X11 O2

Group B R O 3 X21 O4

Group C R O 5 X12 O6

Group D R O 7 X22 O8

2 x 2 Factorial with a PretestPosttest


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Group A R X 11 O1

Group B R X 21 O2

Group C R X 12 O3

Group D R X 22 O4

2 x 2 Factorial Design with a

Posttest Measure


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A Test Market Experimenton Pricing

Sales in Units (thousands)

Regular Price$.99

1301188784

X1=104.75X=119.58

Reduced Price$.89

145143120131

X2=134.75

Cents-Off CouponRegular Price

1531299699

X1=119.25

Test Market A, B, or CTest Market D, E, or FTest Market G, H, or ITest Market J, K, or L

MeanGrand Mean


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Latin Square Design

A balanced, two-way classification schemethat attempts to control or block out the

effect of two or more extraneous factors byrestricting randomization with respect to therow and column effects.


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1 2 3

1 A B C 2 B C A3 C A B

Order of Usage

S U

B J E C T

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